The present invention relates to a lens holder for alignment of a stacked lens module and a manufacturing method thereof, especially to a lens module with a lens holder for alignment formed by injection or press molding of an embedded molding insert that is a stacked lens submodule. This kind of lens module is especially suitable for camera lenses, small lenses, and mobile phone lenses.
The optical lens is a compact optical element in cameras or lenses of camera phones. In practice, the optical element is formed by at least one optical lens. Refer to FIG. 1, an optical lens 20a is made from optical plastic or optical glass and having an optical surface 21a that generally is a round surface, and an outer periphery 22a around the optical surface 21a that can be round or rectangular. In order to fix and package the lens 20a inside a lens module, the lens 20a is glued and fixed in a holding ring (or holder) 10a to form an optical lens set (or assembly) 1a while the holding ring 10a is made from metal or plastic. Thus the lens 20a is aligned with a central axis (optical axis) of the lens module. Moreover, by an actuator, the holding ring 10a (or the optical lens set 1a) moves inside the lens module so as to achieve zoom in/zoom out, as shown in U.S. Pat. Nos. 7,312,933, 7,095,572, US2007/0024989 and JP3650594.
A conventional way of fixing the plastic or glass lens 20a in the holding ring 10a is shown in FIG. 1, especially suitable for glass lens. At first, provide a holding ring 10a according to shape of the outer periphery 22a of the lens 20a such as round or rectangular shape. Then the lens 20a is set into a preset hole of holding ring 10a for being located. Next use glue to fix the lens 20a where the glue is UV glue that requires a curing process such as being radiated in a UV curing oven for curing. Due to compact size of the lens 20a, the optical surface 21a is easy to get scratched or attach with the glue (flow) when the lens 20a is located and fixed by automatic or manual gluing. Thus the processes take time and the yield rate is poor. The curing process of the UV curing glue between the glass lens 20a and the plastic holding ring 10a is especially difficult. Moreover, the curing in the UV curing oven takes long time and the yield rate is poor. Thus the cost is unable to be reduced, as prior arts in JP3791615, JP06-258562, U.S. Pat. No. 7,224,542 and US 2007/0047109.
A technique that places a molding insert in a mold cavity and then treated with injection molding is called a molding insert injection molding method. A molding insert (for example, metal part) is set into a mold cavity of a preset mold. Then inject melt plastic (or rubber) material to fill a preset molding area (material injecting area) and cover whole or part of the molding insert. After cooling and curing, the product is released from the mold. Such manufacturing method is applied broadly to electric elements, connector, mechanical parts and LED, as disclosed in U.S. Pat. No. 5,923,805, TWM313317, and JP07-120610 etc. While manufacturing a cover with plastic lens by such method, the cover (a housing) is used as a molding insert and put into a mold cavity. Then a plastic lens is made by plastic injection and is integrated with the cover. Or use the plastic lens as a molding insert and the cover is made by plastic injection and integrated with the plastic lens so as to form an integrated cover with plastic lens, as shown in TW 0528279 and U.S. Pat. No. 6,825,503. Refer to JP62-251113, the glass plate is used as an molding insert and is covered by plastic material so as to form a window glass or other parts. Refer to U.S. Pat. No. 6,710,945, by two injection holes for plastic material, a molded lens and a lens holder are molded by injection sequentially. Or use infrared gas as the molding insert and produce a mount covering the glass by injection molding. Refer to U.S. Pat. No. 7,332,110, in a press molding, the eyeglass frame is used as an molding insert and is placed into a mold cavity. The preform of the plastic lens is heated to a melt status and then the soft preform is turned into the shape of the cavity by heating and pressing of the mold Thus the preform becomes a lens and integrated with the eyeglass frame to form an eyeglass. However, the press molding technique is unable to be applied to a manufacturing process that integrated the glass lens with the plastic holding ring. Once the plastic holding ring is used as a molding insert, the softening point of the optical glass is about 500° C. that is far more higher than the deformation temperature such as 80° C. of the plastic holding ring. Thus when the temperature of the mold achieves the softening point of the optical glass, the plastic holding ring has already deformed and unable to be molded. Therefore, the press molding is unable to be applied to mass production of the product that uses a plastic holding ring as an molding insert and glass as molding material.
In addition, as to manufacturing of the lens module revealed in US2009/0059398, an optical lens, an alignment fixture and a sensor are mounted into a mold and then inject plastic to form a lens module. Or as shown in FIG. 2, as shown in TWM337077, two optical glass lenses 20b, two light shields 30b, a spacer 40b are used as molding inserts to be mounted into molds 31b, 32b in turn. Then a lens holder together with the above molding inserts being covered form a lens module by plastic injection molding or press molding. However, such technique is unable to be used in the stacked lens submodule already being assembled. Because the stacked lens submodule is an integrated part and is unable to be separated into each single element to be set into a mold. Moreover, the optical axes of the optical lenses 20b, 30b, 40b are difficult to be aligned with one another. It takes time and efforts for alignment of the optical axis and this leads to low production rate and poor precision.
Due to requirement of high precision of the optical lens set for cameras, the lens holder outside a stacked lens submodule needs high precision. The location precision between the stacked lens submodule and the lens holder has great effects on imaging of the lens. Thus how the stacked lens submodule and the lend holder are aligned with an optical axis affects resolution of the images. Therefore, there is a need to develop a new technique applied to assembling of the stacked lens submodule with the lens holder and mass-produce lens modules with good alignment precision by simplified manufacturing processes.